First-Stage Operation

The knee joint is examined by normal arthroscopy. A cartilage lesion is detected, and a decision is made to treat the defect by ACI. Often such a decision is made based on an earlier treatment that failed.^1,2,3

ACI could subsequently be regarded as a second line of treatment option. All types of joints can be treated, but the most treated joints have been the knee joint and the ankle joint. The technique is the same regardless of the joint treated. However, in this chapter the description is for the knee joint.

Cartilage Harvest

The cartilage is harvested from a less loaded weight-bearing area such as the upper medial femoral condylar area or similar on the lateral upper femoral trochlear area. Also the notch area is easy to use for harvest (Fig. 9C-1).

FIGURE 9C-1 The suggested locations for harvest of cartilage for cell culture.

By long-time experience, the amount that has been suggested for cartilage harvest is 200 to 300 mg. Such an amount is about a strip with 10 mm in length and 5 mm in width.

Use a ring curette or sharp gouge like a Wiberg raspatorium. Go deep down to cartilage-bone junction and leave a thin attachment of the strip. This strip may then be grasped with a forceps and ripped off with a gentle movement and taken through the portal to be put into a tube with saline. You may need two to three similar strips (Figs. 9C-2 and 9C-3).

FIGURE 9C-2 With the raspatorium, go down deep to bone to obtain a strip of cartilage for cell culture. Leave the last part of the strip still attached. Use a grasping forceps to rip off the strip and pull out from the knee portal.

FIGURE 9C-3 About two to three strips are harvested and put into a transport medium.

For the cell culture, the staff needs to take 10 6-ml test tubes with blood to be processed into serum for the subsequent cell culture.

Blood test tubes and harvested cartilage are sent to the cell laboratory that the hospital has a contract with.

Second-Stage Operation

The knee joint is opened by a miniarthrotomy.The cartilage defect is debrided (see Chapter 3). The debridement should result in a well-delineated defect, slightly oval.

Lesion Measurement

The size of the defect is measured using a sterile packaging of the sutures as a template. If any bleeding is observed in the bottom of the defect, hemostasis with cotton pads soaked with epinephrine (1:100 epinephrine in 20-ml sterile saline) may be used.

Harvest of the Periosteum

For the first generation of ACI, periost is to be harvested. The periosteum is harvested through a separate incision from the proximal medial tibia, just distal to pes anserinus (Fig. 9C-4).

FIGURE 9C-4 The periosteal patch is obtained from the upper medial tibia, distal to the insertion of the pes anserinus.

With the template in place, the periosteum could be sized and cut with a scalpel and harvested sharply with a periosteal elevator and carefully released from the bone.

It is very important that a thin periosteum without remaining fibrous tissue is harvested.

Positioning and Suturing of the Periosteum

The received periosteum is positioned over the defect with the part that has been attached to the bone, the cambium layer facing the cartilage defect.

The periosteum is sutured to the defect with interrupted sutures (Vicryl Ethicon, Inc., Somerville, N.J. or Dexon. [Coviden, Mansfield, MA]) 5-0 or 6-0 sutures (Figs. 9C-5 and 9C-6). The sutures should be immersed in sterile glycerin or drawn through the patients’ fatty tissues.

FIGURE 9C-5 The periosteum is sutured to the defect with inter-ruptured sutures with an interval of approximately 3 to 4 mm. Angle the suture needle toward the periosteal membrane approximately 2 mm from its edge and pass through the membrane into the adjacent cartilage wall following the curvature of the used needle. Enter the cartilage about 2 mm below the surface with a 3- to 4-mm bite.

FIGURE 9C-6 Example of a large femoral condylar defect covered with a periosteum.

Interruptured sutures are used with an interval of approximately 3 to 4 mm.

Start with one suture in each corner of the defect except for the trochlear region where sutures are placed directly after each other. Angle the suture needle toward the periosteal membrane approximately 2 mm from its edge, and pass the through the membrane into the adjacent cartilage wall, following the curvature of the used needle. It is advisable to enter the cartilage about 2 mm below the surface and with a 3 to 4 mm bite (Fig. 9C-5).

Use fibrin glue to seal the suture line in order to minimize leakage of cells. One may also fill the bottom of the defect with fibrin glue to get an even distribution of the cells when implanting the cells under the membrane.

Implantation of Cultured Cells in Suspension

The cultured chondrocytes are finally implanted into the defect under the membrane. A final suture is put at the implantation entrance after implantation and some extra fibrin glue (Figs. 9C-7 and 9C-8). The aim is to implant 30 million cells/ml or at least 2 million cells/cm² (Fig. 9C-9).

FIGURE 9C-7 The defect has been covered by a periosteal or collagen membrane. The suture line is filled with fibrin glue to minimize the leakage of cells. The cell suspension is finally injected into the water-tight sealed defect.

FIGURE 9C-8 A patella defect covered by a sutured collagen membrane. Cells are injected into the defect, under the membrane.

FIGURE 9C-9 A syringe with chondrocytes in suspension. The aim is to implant 30 million cells/ml or at least 2 million cells/cm².

Wound Closure

Close wounds as one would for a normal arthrotomy. No drainage is used intraarticularly. If wanted, the drainage can be placed extra capsular.

Noncontained Lesions

If the defect is not well contained, the membrane can be sutured to the synovial lining if near the notch. At other regions, suture anchors may be needed. If the uncontained lesion has thick walls, mosaicplasty plugs can be used to build up the missing wall, making the defect into a contained reconstructed defect.

Large Defects and Defects with Concomitant Malalignment

Consider doing a concomitant unloading osteotomy (see Chapter 13). Prepare the defect as described previously until cell implantation. (See first page of this chapter “Technical Overview.”) Do the osteotomy operation, and finish with implantation of the cells (Fig. 9C-10).

FIGURE 9C-10 An ACI chondral defect treated at the same time with an unloading opening wedge osteotomy.

Second-Generation ACI

The second-generation ACI is an exchange of the periosteal membrane to instead use a collagen membrane⁴ such as the Chondro-Gide membrane (Chondro-Gide Geistlich Surgery, Wolhusen, Switzerland). The membrane has to be cut in the exact size because, in comparison to the periosteum, it does not stretch much. Otherwise, the same technique used for the periosteum can be used for membranes.

Postoperative Management

There exists no consensus for the postoperative rehab (see also Chapter 16). The rehabilitation guidelines have changed during the years since the first ACI was done in 1987.

The short description that follows is my personal recommendation for ACI and similar repair techniques. For more specific information and discussion about the rehabilitation, look also at the Postoperative Cartilage Repair Rehabilitation chapter (Chapter 16).

The extremity is immobilized in a brace and locked in extension for 2 weeks. Full weight bearing is allowed in the brace as pain allows. After 2 weeks, the brace is used outdoors, unlocked, for another 4 weeks.

A very large defect may be protected by an unloader brace for a longer period. One may even consider performing a concomitant permanent unloading with osteotomy (Fig. 9C-10).

Open chained knee strengthening should occur from approximately 8 weeks. Running is not advised until 9 to 10 months postsurgery.

High-level activities should not be performed until 12 to 14 months postoperatively.